Acer pseudoplatanus: A Potential Risk of Poisoning for Several Herbivore Species

Abstract

Acer pseudoplatanus is a worldwide-distributed tree which contains toxins, among them hypoglycin A (HGA). This toxin is known to be responsible for poisoning in various species, including humans, equids, Père David’s deer and two-humped camels. We hypothesized that any herbivore pasturing with A. pseudoplatanus in their vicinity may be at risk for HGA poisoning. To test this hypothesis, we surveyed the HGA exposure from A. pseudoplatanus in species not yet described as being at risk. Animals in zoological parks were the major focus, as they are at high probability to be exposed to A. pseudoplatanus in enclosures. We also searched for a toxic metabolite of HGA (i.e., methylenecyclopropylacetyl-carnitine; MCPA-carnitine) in blood and an alteration of the acylcarnitines profile in HGA-positive animals to document the potential risk of declaring clinical signs. We describe for the first instance cases of HGA poisoning in Bovidae. Two gnus (Connochaetes taurinus taurinus) exposed to A. pseudoplatanus in their enclosure presented severe clinical signs, serum HGA and MCPA-carnitine and a marked modification of the acylcarnitines profile. In this study, even though all herbivores were exposed to A. pseudoplatanus, proximal fermenters species seemed less susceptible to HGA poisoning. Therefore, a ruminal transformation of HGA is hypothesized. Additionally, we suggest a gradual alteration of the fatty acid metabolism in case of HGA poisoning and thus the existence of subclinical cases.

Detection of Hypoglycin A and MCPrG Metabolites in the Milk and Urine of Pasture Dairy Cows after Intake of Sycamore Seedlings

“…The outcome is contrary to that in Père David’s deer in two Zoo’s in Germany as well as gnus in a Zoo in France which developed clinical signs with a rapid progression comparable to those also observed in horses. − Several publications report that already relatively small amounts of maple toxins may be sufficient to poison equids. ,, Maple toxin poisoning in horses results in muscular weakness and stiffness following respiratory depression and recumbency leading to death within 72 h Complementary myoglobinuria is also a common clinical sign in horses and was also seen in poisoned deer with fatal course …”

“…7,30,50 A shorter retention time, as suspected in camelids and sheep, therefore might result in HGA absorption depending on feed availability or exposure to the toxins, as proved by the detection of HGA in serum of sheep and goats. 7,32 In contrast, however, the toxins could have a short retention time in the rumen due to their hydrophilicity and a following quick transition to the liquid phase if they are quickly released from the plant matrix.…”

“…HGA and MCPrG represent, as amino acids, hydrophilic and soluble substances that can already be utilized by microbes in the rumen. Additionally, due to a high ruminal retention time in large ruminants, it is therefore reasonable to assume that HGA and MCPrG probably do not reach the site of their absorption, the proximal small intestine, in sufficiently high concentrations. ,, A shorter retention time, as suspected in camelids and sheep, therefore might result in HGA absorption depending on feed availability or exposure to the toxins, as proved by the detection of HGA in serum of sheep and goats. , In contrast, however, the toxins could have a short retention time in the rumen due to their hydrophilicity and a following quick transition to the liquid phase if they are quickly released from the plant matrix.…”

“…However, to our knowledge, there is neither a direct proof that dairy cows ingest sycamore seedlings nor are there data on metabolism and excretion of maple toxins by dairy cows available. For ruminants in general, toxic effects caused by HGA/MCPrG have only been demonstrated in the browsing Père David’s deer, gnus, and Bactrian camels, − while there are no known cases of poisoning in grazers like sheep or intermediate types like goats. , Gonzalez-Medina et al detected HGA in serum samples from ewes and their lambs and also MCPA conjugates in one ewe at 0, 2, and 7 days after grazing on a pasture with sycamore seedlings. No animal in this case showed any adverse effects, suggesting a low (or even no) sensitivity for the toxins in sheep.…”

“…Physiological and gastrointestinal peculiarities in ruminants could result in low sensitivity to the toxic effects of certain plant toxins . For example, due to the large size of the rumen as well as the long retention time, ruminal transformation of HGA might occur before entering the proximal small intestine as the site for HGA absorption. , Firstinsights into the effects of the rumen microbiome on detoxification, although, showed no significant decrease in HGA concentrations but rather an increase of yet unknown cause over a short period of 2 h of in vitro incubation in ruminal fluid of adult sheep …”